For the 2021 GMC Sierra 2500HD, the low-beam and high-beam headlights both use a D5S bulb. The supplied fitment data does not identify a separate bulb difference between the two headlight functions or specify a projector versus non-projector variation.
Other useful lighting applications include:
- Fog lights: 5202 LED
- Front turn signals, parking lights, brake lights, tail lights, and rear turn signals: 7443
- Center stop light and trunk light: 921
- License plate lights: 2825
- Rear side markers: 194
Confirm the bulb location before ordering, particularly when replacing a D5S headlight bulb or the 5202 LED fog-light bulb.